The demands for supporting and producing different services has directed the development of data communication networks in the direction of a so-called intelligent network IN. An intelligent network is an architecture the purpose of which is to offer modular operations independent of the service used, which operations can be connected to each other as components when creating new services, whereby the determining and planning of the new services is easier. The second object is to be independent of a telecommunication network in the supply of the services. The services would be separate from the lowest physical network structure, in which case they can be distributed.
The so-called Basic Call State BCSM has been defined for the intelligent network. It is a description of the functions of the call control function CCF, which are needed for the setting up and maintaining of the connection route between the users. Thus BCSM offers the framework for the description of those basic call and connection events which can lead to the IN service logic to become active; in other words it detects those detection points DP in a call process and connection process in which the call control can be in an interaction with the IN service logic object and in which the transfer of the control can take place.
Also, other network architectures have been presented in which the objective is to separate the network control from the telecommunications network. One of such architectures has been described in PCT application WO93/05599. The control function system of the network has been separated from the call control, but the solution requires to construct the network from the outset according to the presented operating principle and it does not provide information as to how the present public switched telephone network PSTN could be connected to the network in accordance with the application.
The architecture idea that has been presented in the aforementioned PCT application can be developed further. Architecture, in which various traditional call processing functions, such as switching fabric or channel control, call control, and connection control are separated into distinct application processes, is described in European patent applications EP-0631456 and EP-0631457.
Architecture similar to that described in EP-applications, i.e. architecture, in which the handling of connection means and other network resources possibly needed by the call is totally separated from the handling of the transmission of messages between the parties of the call (end-users) and service itself, has been proposed by Telecommunications Information Network Architecture Consortium, TINAC. The parties of the call first discuss what kind of network resources they need, and the network resources are reserved and given to use only when they are really needed. This makes separate development of transmission resources and connection resources and services possible. Then, the network control can use services irrespective of the network technology. The same service can be produced with different techniques. For example, the voice message service can be produced using ATM VC or a narrow band ISDN network. In the proposed architecture, the services comprise a group of interactive service components. Some components are service specific and can use services offered by the general service components. The general service components offer services which are related to the processing of different types, communication services, for example audio and video, and special resource services, for example conference rings.
In this architecture, the connections are handled by Connection Management, the control software called Communication Management is responsible for the communication, and the control software called Service Management carries out the service.
The proposed operation is of such nature that when a service is used, the Service Management gives to the Communication Management a description of the desired communication status, which corresponds to the requested service. The Communication Management determines what the connection status must be in order to reach the given communication status. It provides the Connection Management with the description of the connection status, in which case the Connection Management makes the connections so that the desired connection will be established. The concepts of communication status and connection status are briefly described in the following. The communication status is based on the concept called Logical Connection Graph, LCG. The Service Management specifies the communication resources needed as "Logical Connection Graph" terms, irrespective of the network structure and technique.
The information model, shown in FIG. 1 of the attached drawings, presents in a simplified manner what the communication status refers to. The stream interfaces represent abstractions of the devices, and the binding interfaces represent abstractions either of the local connections or of the long distance connections. Both are controlled through the corresponding operational interface, which offers functions for the beginning, modification and deletion of the objects. The figure represents the parties of the communication and their interfaces, when the parties are engaged in the communication session. The stream is a unidirectional bit flow having a given frame structure (format, coding) and the quality of service QoS parameters, which determine the time alignments of the frames, synchronizing demands between the steams, etc. The communication session management CSM provides the interface for specifying the bindings of the stream interfaces explicitly and for control of the bindings. A stream binding object defines the relationship between the stream interfaces. Virtual devices are abstractions of actual physical devices. Streams are unidirectional point to point or point to multipoint, that is, they consist of one or more branches. A stream branch is defined between the producer and each customer. Logical Connection Graph LCG is equivalent to stream binding. It comprises logical vertexes connected by the logical lines through a logical gate.
FIG. 2 shows the contents of FIG. 1 as LCG concepts. LCG is not interested in the location of the resources in the network. It is needed for the defining of the operations which control stream bindings in order to specify the interface offered by the CSM. In other words, it must know the communication status as LCG concepts so that the communication session management CSM can operate.
To be able to operate perfectly, CSM needs to be provided with a description of the connection status. The concepts of physical connection graph PCG, which represents the network connections, and the nodal connection graph NCG, which represents the configuration of the resources of the nodes have been derived from the LCG. The term "physical" refers to the network and the term "nodal" refers to the nodes between which the network establishes the connections.
The difference between the physical and the logical graph lies in the fact that the logical configuration of the connection resources does not pay attention as to where the resources are, whereas the physical configuration is aware of their location. The logical connection graph LCG represents an end to end connection between computational interfaces and the physical connection graph PCG represents a connection between network termination points. The computational interfaces can be in this context of current type or functional. The essential point of the new architecture is that they can be of stream type. There is a conversion from the logical addresses of the logical connection graph into a physical address of the physical connection graph. The conversions from the logical lines into physical lines exist likewise. Several LCG elements can be grouped as one element by multiplexing or a few LCG elements can be converted into several physical elements by decomposition.
When the new network architecture presented above is brought into use, a problem will arise as how to adapt the new architecture to the existing network such as the intelligent network. One solution is to bring the described network architecture into use in some overlay network, such as an ATM or other broad band network, and to match this new network with an existing network without changing the architecture of either one. The integrated use would be carried out possibly by means of a separate adaptation program and separate hardware. The adaptation program can be inserted in the new architecture, in which case changes in existing systems are not needed.
A drawback of the solution presented above is that with the integrated use of the networks it is not possible to utilize the software technology, which would open the network to an open software competition. Thus, the integrated use does not offer alternative ways to utilize in the best way the proposed new architecture and the existing architecture. The solution based on the integrated use leads to the fact that the standardization of the existing networks and the proposed new network would have to be pursued side by side.